Practically all vehicles presently on the market comprise, in the front of the vehicle, seats with a back portion the inclination of which is adjustable in order to increase the passenger safety by adapting the seat to the morphology of the passenger, and to permit, for two-door vehicles, a folding of the back portion of the seat onto the sitting portion for allowing passengers access to the rear of the vehicle with a single back seat or individual seats.
Mechanisms permitting these various movements of the back portion of the front seat have been known for a long time, but these mechanisms are both rather complex and fragile.
It is therefore an object of the present invention to provide a mechanism in the form of a single-roller locking device that is inexpensive, exhibits no play and Yet is very strong, easy to manufacture and very reliable so that by locking the device it resists impacts, frontal as well as lateral, without the respective mechanism being released, thereby providing a high degree of safety for the passengers seated on the seat.